Here I am going to share few answers related to Test Classes, which is being asked many times to me by novice Programmers. Please feel free to post Comments if your question is not answered here. I will try my best to add those Questions in this article. If you want to learn Test Class from very basic, you can check this article also.

Well, It differs from person to person, as every programmer has its own style of writing code. However I will list few of mine.

Very important and first, “Test Coverage Target Should not be limited to 75%”. It is not about coverage, It is about testing complete functionality. It will be always better if your code fails during test execution, It will be less devastating than failing functionality after product release.

If possible Don’t use seeAllData=true, Create your Own Test Data.

Always use @testSetup method dedicated to create test records for that class. This is newly added annotation and very powerful. Any record created in this method will be available to all test methods of that class. Using @testSetup method will improve test execution performance by creating test records only once for that class. If you are not using this, means test record is created in each TestMethod which will be very slow. Read this Salesforce documentation for more information.

Create Different Class which will create Dummy Data for testing, and use it everywhere (You have to be very careful, as sometimes it may slow down test class execution by creating unnecessary data which does not require by every test methods. So few developer prefer test data creation per Test class)

If your Object’s Schema is not changing frequently, you can create CSV file of records and load in static resource. This file will act as Test data for your Test Classes.

Use As much as Assertions like System.AssertEquals or System.AssertNotEquals

Use Test.startTest() to reset Governor limits in Test methods

If you are doing any Asynchronous operation in code, then don’t forget to call Test.stopTest() to make sure that operation is completed.

Use System.runAs() method to enforce OWD and Profile related testings. This is very important from Security point of View.

Always try to pass null values in every methods. This is the area where most of program fails, unknowingly.

Use Test.isRunningTest() in your code to identify that context of class is Test or not. You can use this condition with OR (||) to allow test classes to enter inside code bock. It is very handy while testing for webservices, we can generate fake response easily.

@TestVisible annotation can be used to access private members and methods inside Test Class. Now we don’t need to compromise with access specifiers for sake of code coverage.

End your test class with “_Test”. So that in Apex Class list view, Main class and Test class will come together, resulting easy navigation and time saver.

Use of SmartFactory to auto generate test data

This is very common pattern where we create test data in some utility method ans reuse it across test methods. However change in requirement is inevitable and many validation rules and mandatory fields gets introduced in application and test methods starts breaking. We can resolve this issue by using unmanaged package available on github which creates Test data and hierarchy automatically using dynamic Apex and make sure all required fields are populated.

Just use SmartFactory in your tests to create objects:

Account account = (Account)SmartFactory.createSObject('Account');

To cascade and create objects for lookup and master-detail relationships:

How to write Test method of Controller Extension for StandardSetController ?

In Same way, with few modification :

//Lets Assume we are writing Controller extension to use on List View of Account
List <Account> acctList = [SELECT ID FROM Account];
//Start Test Context, It will reset all Governor limits
Test.startTest();
//Inform Test Class to set current page as your Page where Extension is used
Test.setCurrentPage(Page.YOUR_PAGE);
//Instantiate object of "ApexPages.StandardSetController"by passing array of records
ApexPages.StandardSetController stdSetController = new ApexPages.StandardSetController(acctList);
//Now, create Object of your Controller extension by passing object of standardSetController
YOUR_Extension ext = new YOUR_Extension(stdSetController);
//Here you can test all public methods defined on Extension "ext"
//..... your code
//Finish Test
Test.stopTest();

Why getSelected() method of StandrdSetController is not returning anything?

You might be in situation that getSelected() method is not returning anything in your test method inspite of proper coding. In Actual scenario we select records in ListView and after clicking on custom button, StandardSetController’s getSelected() method returns selected record in Controller Extension. So, to Select records programmatically in Test method we have to use method “setSelected()” as shown in below code.

//Lets Assume we are writing Controller extension to use on List View of Account
List <acctList> = [SELECT ID FROM Account];
//Start Test Context, It will reset all Governor limits
Test.startTest();
//Inform Test Class to set current page as your Page where Extension is used
Test.setCurrentPage(Page.YOUR_PAGE);
//Instantiate object of "ApexPages.StandardSetController" by passing array of records
ApexPages.StandardSetController stdSetController = new ApexPages. StandardSetController(acctList);
//Here, you are selecting records programmatically, which will be available to method "getSelected()"
stdSetController.setSelected(acctList);
//Now, create Object of your Controller extension by passing object of standardSetController
YOUR_Extension ext = new YOUR_Extension(stdSetController);
//Here you can test all public methods defined on Extension "ext"
//..... your code
//Finish Test
Test.stopTest();

Any sample Template for method or class which generates Dummy Data?

You can create methods something like below to generate TestRecords. It will change on requirement however will give some idea.

How to check Error Page Messages in Test Classes to ensure that messages are displayed as expected on Visualforce Page ?

Assume that you have one Controller class which adds error message to Visualforce page.

public class DemoController
{
//... some code
public PageReference somemethod()
{
//Check for some validation. like User is Authorized or not ?
if(!validate())
{
//Means User is not Authorized for this operation, Add error on Visualforce page
Apexpages.addMessage( new ApexPages.Message (ApexPages.Severity.ERROR, 'User is not Authorized to perform this Operation'));
return null;
}
return Page.SomePage;
}
}

Now, lets say you want to check whether error message is added on visualforce page or not in Test Class.

2. TestVisible Annotation : With this annotation, you donâ€™t have to change the access modifiers of your methods and member variables to public if you want to access them in a test method. For example, if a private member variable isnâ€™t supposed to be exposed to external classes but it should be accessible by a test method, you can add the TestVisible annotation to the variable definition.

3. Data Generation : for testMethods

Like wise you said, create a different class for dumping data to your testclass like say DataUtil class that creates objects , then use a wrapper on top of it. For each project you can make project specific helper class like if you working on New Lead Process process design then design a new helper like testNewLeadProcessController class which in turn call you ‘DataUtil class’ this makes it easier to maintain project specific testclasses

It would awesome if you explain a little more on ‘ Error Page Messages in Test Classes’ when and how is this used . Why can’t we de-couple it to a separate Error handler class, if my understanding is purely wrong, then please correct me

It would awesome if you explain a little more on ‘ Error Page Messages in Test Classes’ when and how is this used . Why can’t we de-couple it to a separate Error handler class, if my understanding is purely wrong, then please correct me